A magnetic disk device as an example of a disk device incorporates a magnetic disk in a housing, a rotary spindle motor supporting and rotating the magnetic disk, a magnetic head for reading/writing data from/to the magnetic disk, and a carriage assembly supporting the magnetic head so that the head can move relative to the magnetic disk. The head section of the magnetic head includes a magnetic recording head for writing and a reproducing head for reading.
To increase the recording density and capacity of a magnetic disk device or reduce its size, magnetic heads for perpendicular magnetic recording have recently been proposed. In one such magnetic head, a recording head comprises a main pole configured to produce a perpendicular magnetic field, a write shield pole, and a coil. The write shield pole is located on the trailing side of the main pole with a write gap therebetween and configured to close a magnetic path that leads to a magnetic disk. The coil serves to apply a magnetic flux to the main pole.
In a conventional recording head and magnetic recording device for imbricate recording, an increase in the intensity of the recording magnetic field applied to a recording medium is realized by increasing the width of the main pole compared to the recording track pitch, thereby enabling recording on the medium with a greater coercive force. Further, since the magnetic recording head has a structure of a main pole, a trailing shield TS, a leading shield LS and side shields SS, the gradients of the recording magnetic field in both a down-track direction and a cross-track direction can be increased. As a result, the recording densities in the down-track direction and cross-track direction can be increased to thereby increase a surface recording density.
A magnetic recording head for high-frequency assist recording, which includes a spin-torque oscillator provided as a high-frequency oscillator between the main pole and the write shield (i.e., in the write gap), has also been proposed. Also in this magnetic recording head for high-frequency assist recording spin-torque oscillator, the recording magnetic field and the high-frequency magnetic field can be increased in intensity by increasing the width (cross-track directional width), thereby enabling recording on a recording medium with a greater coercive force. In this case, however, the gradient of the high-frequency magnetic field in the cross-track direction is small, which makes it difficult to increase the recording density in the cross-track direction.